There is an imaging device such as a single lens reflex digital camera including a camera body and an interchangeable lens unit to be integrated with the camera body. Such a digital camera can allow a user to select a desirable lens type with a certain angle of field or brightness and mount the lens in the camera body with an image sensor of a large capacity to capture images with high sensitivity without a large amount of blur or noise. A camera body of such a digital camera comprises an image sensor and an image processor (image processing engine).
Generally, types of the lens unit combinable with the camera body are limited in most single lens reflex digital cameras. In order to solve this, Japanese Laid-open Patent Publication No. 2006-54709 (Reference 1) discloses an imaging device which comprises a lens unit including an image sensor and an image processor to generate image data in predetermined format to transmit the data to a camera body, for example. Thereby, various kinds of lens units can be combined with the camera body, improving versatility of the camera body and the lens unit.
For another example, Japanese Laid-open Patent Publication No. 2000-32308 (Reference 2) discloses an imaging system which comprises an interchangeable imaging unit (equivalent to the lens unit) with an image sensor to generate image data of a subject and a data processor (equivalent to the camera body) connected with the imaging unit to process the image data. With such a configuration, an imaging system with a downsized imaging unit and high-speed image data processing can be achieved.
The imaging device in Reference 1 is composed of a camera head (equivalent to the interchangeable lens unit) with an image sensor and a camera body. A digital signal processor (image processor) is provided in each of the camera head and the camera body. Image signals are transmitted from the camera head to the camera body in JPEG format only. Accordingly, the camera body can perform image processing irrespective of the camera head.
With such a configuration, various kinds of lens unit can be mounted in a single camera body. However, there is a problem that the format of image data from the camera head to the camera body is fixed to JPEG format, limiting the types of format of images storable in the camera body. In storing image data in format other than JPEG, compressed image data has to be decompressed and then reprocessed (recompressed), which deteriorates quality of images.
Therefore, the imaging device in Reference 1 needs to include communication lines between the camera head and the camera body which can deal with the maximum amount of captured image data since the device cannot change processes which the image processors of the camera head and of the camera body perform in accordance with an operational state of the device.
Meanwhile, the imaging system in Reference 2 is configured that the imaging unit processes output signals of the image sensor to generate image data and transmits it to the data processor. The data processor includes a display unit displaying received image data and a storage unit to store image data.
This imaging system does not need a circuit dedicated for image processing in the imaging unit, preventing increases in circuit scale and manufacturing costs. However, since analog signals of the image sensor are transmitted from the imaging unit to the data processor, they need to be transferred by low voltage differential signaling (LVDS), especially with use of CMOS as an image sensor. This results in increasing the number of communication lines by about 20%.